Modern users rely on global navigation satellite system (GNSS) enabled personal navigation devices (PNDs) or other GNSS-equipped electronic devices such as cell phones to navigate while in motion. Consequently, users require a high degree of accuracy in a wide range of navigation scenarios. However, effective GNSS-based navigation is reduced in areas where signal transmission is hindered, such as in tunnels, or in ‘urban canyons’, where signal transmission is reduced by artificial canyons formed by surrounding buildings.